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Mapping the topological phase diagram of superconducting qubit systems

Pedram Roushan, UCSB

(Session 10 : Saturday from 9:15am - 9:45am)

Building a practical quantum simulator requires a scalable architecture suitable for large numbers of qubits. By combining the high coherence Xmon qubits with an adjustable inductance, we have developed a new qubit architecture called g-mon, which has a tunable qubit-qubit interaction. To demonstrate this tunability, we have performed high fidelity single and two-qubit gates. Turning on the qubit-qubit interaction allows for fast multi-qubit operations implemented in less than 30 ns, achieving multi-qubit gate times approaching that of single qubit gates. Furthermore, we show the versatility of this system by mapping the topological phase diagram of interacting Hamiltonians. So far, experimental studies of topological invariants in condensed matter systems have been limited to transport measurements in non-interacting systems. Recently, it was proposed [1] that the topological properties of Hamiltonians can be inferred from quantum dynamics. Using superconducting g-mon qubits, we experimentally measure the Berry curvature, a quantity that reflects the geometrical properties of the eigenstates, for various eigenstates of the Hamiltonian of the system. We will discuss the phase diagram of various topological phases and the robustness of the measured Chern numbers. [1] Gritsev and Polkovnikov, PNAS, 109, 6457 (2012).